Physical exercise benefits the general health of the human body. For example, physical exercise can bring about enhanced muscle tone, decreased body fat, increased cardiovascular health, increased mental health, reduction of the effects of stress, etc. In addition, physical exercise may bring about increased cognitive abilities, including an increased ability of the brain to form and retain memories. For example, research has shown that physical exercise can increase the production of some neurotrophic factors, or proteins that are capable of signaling neurons to survive, to differentiate, to grow, etc. (see, e.g., “Exercise: a behavioral intervention to enhance brain health and plasticity” by Cotman and Berchtold, Trends in Neuroscience, 2002). In particular, Cotman finds that rats or mice that participate in voluntary “wheel running” produce increased levels of brain-derived neurotrophic factor (BDNF) (among other proteins) in their hippocampus. BDNF has been found to be an important neurotrophic factor for developing long-term memory, and the hippocampus is normally associated with higher cognitive function, such as learning and memory. As such, physical exercise, which induces the production of BDNF and other proteins, may also enhance learning, including the ability to record and retain memories.